The present invention relates to a method for fabricating a capacitor; and, more particularly, to a method for fabricating a ferroelectric capacitor.
As integration of a semiconductor device increases, a capacitor having a high charge capacity in a small space and a low leakage current to obtain good electric characteristics of the capacitor has been required. A ferroelectric layer, such as a SBT (SrBi2Ta2O9) layer, a PZT layer or the like, has been used in the capacitor. Also, a Pt layer having good electrical characteristics is used as an electrode material.
When a semiconductor device having a plug, which is a conductive layer, such as a polysilicon layer, is fabricated by using the ferroelectric layer, thermal treatment processes for crystallization of a ferroelectric layer and for recovering remnant polarization are required. At this time, the thermal treatment processes cause thermal deterioration and oxidation of the plug so that contact resistance increases. Accordingly, reduction of the thermal treatment temperature is required below 650xc2x0 C.
The recovery thermal treatments are performed for recovering a thermally deteriorated ferroelectric characteristic caused by plasma impact. Since it is an important issue to decrease the temperature of the recovery thermal treatments, the recovery thermal treatments are performed with two steps. A first step is performed after forming an electrode and a second step is performed after forming a contact hole for a metal wire.
In the case of the second step, an insulating layer for planarization, which is formed on the plug, prevents that the plug is thermally deteriorated, however, in case of the first step, the plug is thermally deteriorated and oxidized by oxygen diffusion through sidewalls of the capacitor. Conventionally, the first step is performed after a top electrode, a ferroelectric layer and a bottom electrode are etched.
When the first recovery thermal treatment is performed, since plasma impacts are caused by etching processes of the top electrode, the ferroelectric layer and the bottom electrode have to be removed, a high thermal treatment temperature is needed so that thermal deterioration and oxidation of the plug are caused and recovery of the ferroelectric characteristic is decreased.
It is, therefore, an object of the present invention to provide a method for fabricating a capacitor capable of improving the electrical characteristics thereof by preventing oxidation of a plug by reducing the temperature of a thermal treatment process.
In accordance with an aspect of the present invention, there is provided a method for fabricating a capacitor comprising the steps of: a) performing a planarization process after forming a diffusion barrier on a semiconductor substrate including a plug and a silicide layer; b) depositing an adhesion layer on the entire structure and exposing the diffusion barrier by a selectively etching process; c) sequentially depositing a bottom electrode, a ferroelectric layer and a top electrode on the entire structure; e) forming a top electrode pattern by performing a plasma etching process and a first recovery thermal treatment process; and f) forming a ferroelectric layer and bottom electrode patterns by performing a plasma etching process and a second recovery thermal treatment process.